The overall objective of this core project is to determine the in vitro antiviral efficacy of phosphonate analogs of ganciclovir (DHPG) and of benzothiophene analogs provided by Project 1. Compounds with significant activity against human cytomegalovirus (HCMV) will be selected for follow- up study of their efficacy against other herpesviruses [murine cytomegalovirus (MCMV), varicella-zoster virus (VZV), herpes simplex virus types 1 and 2 (HSV-1, HSV-2) and human herpesvirus 6 (HHV-6)] and for other studies designed to define the observed activity. the long-range goal is to provide drugs that will be effective in treating HCMV opportunistic infections associated with acquired immunodeficiency syndrome. The specific aims for this research project are to (1) Prepare the new test compounds in the appropriate formulation and evaluate their in vitro antiviral activity against HCMV by using a plaque reduction test. Toxicity, virus (placebo), and normal controls will be included, as well as a known active drug for comparison purposes. (2) Accomplish follow-up studies of active compounds by virus yield reduction assays, and run antiviral experiments against a recent HCMV clinical isolate, a DHPG- resistant HCMV isolate, a foscarnet-resistant HCMV, and MCMV. The experiments will use plaque reduction for the human viruses and inhibition of viral-induced cytopathic effect for the murine virus. For compounds found to have significant antiviral activity, (3) Perform cell viability assays (trypan blue exclusion) and radiolabeled metabolic precursor incorporation into cellular DNA, RNA, and protein to determine 50% cytotoxic doses. (4) Ascertain the stage of viral replication affected by running timing studies to determine whether HCMV-specific early antigen, DNA synthesis, or late antigen production is inhibited. (5) Run in vitro experiments against VZV, HSV-1, HSV-2, and HHV-6 to determine the breadth of antiherpesvirus activity shown by these HCMV inhibitors. (6) Run in vitro interferon induction studies to further characterize the activity of selected positive benzothiophenes. (7) Evaluate selected active compounds with one another or with DHPG or foscarnet in in vitro combination experiments against HCMV.